Inside Austin Butler’s grueling workout routine that took his body to ‘the next level’

Austin Butler’s personal trainer revealed how the actor transformed his body in just 14 weeks.

Fitness instructor Roy Chan detailed the grueling workout routine and nutrition plan that helped the actor get in tip-top shape in a post shared to his Instagram last week.

“We started our journey in April and the following images show what 14 weeks of smart, consistent work can do,” Chan wrote alongside images of Butler’s rippling six-pack abs and bulky muscles.

The gym coach explained that Butler combined “technical movement” and “whole-food nutrition” with “timeless training principles” to get him in “peak shape.”

Chan also said that his methods helped the “Elvis” star “build habits that last a lifetime.”

“When Austin came to me after wrapping ‘Caught Stealing,’ he saw it as the perfect moment to take his body and health to the next level,” Chan recalled. “This wasn’t just about prepping for another role; it was about building a sustainable foundation for long-term peak performance.”

Chan noted that they had just 14 weeks to prepare Butler for two big projects — his role in the upcoming crime film, “Enemies,” and his shirtless cover shoot for Men’s Health.

“From the start, we agreed that becoming one of the greats is a long game,” Chan wrote. “You can’t sacrifice health and wellness every time a new aesthetically demanding role comes along.”

The health honcho made a promise to Butler that they would “take a different approach that prioritized strength and longevity” to transform his physique.

“So proud of you @austinbutler,” Chan gushed.

Several videos captured Butler, 34, engaging in all different types of exercises, ranging from running and biking to weight-lifting and lunges.

Chan’s insight comes shortly after Butler opened up about how he accomplished his thicker bottom to portray a baseball player in “Caught Stealing.”

“I actually have a whole section of just baseball players’ asses that [filmmaker Darren Aronofsky] would send me,” Butler told Men’s Health in his cover story, which was published Aug. 19.

“He was like, ‘Look how thick they are!’”

Butler explained that he did “a ton of hip thrusters” to beef up his caboose.